Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 700 PM EST Mon Mar 06 2023 Valid 12Z Fri Mar 10 2023 - 12Z Tue Mar 14 2023 ...Model Guidance/Predictability Assessment/Pattern Overview... Recent GFS runs have come into much better agreement with the ECMWF over Alaska as the medium-range period begins this Friday in a blocky upper-level pattern following the break down of a highly amplified ridge over the vicinity. The 12Z ECMWF offers the fastest solution regarding the upper shortwave digging south into the Gulf of Alaska on Friday. This solution may be too fast as its 00Z and 12Z ensemble means are not quite as fast. Both deterministic solutions and ensemble means agree well that a piece of the upper ridge will break off and retrograde toward/south of the Aleutians as a couple of shortwaves around the top side of the ridge. The first shortwave, being the one mentioned above, will tend to dig and amplify as it swings back to the east and heads toward the Panhandle during the weekend. Again, the 12Z ECMWF offers the deepest and fastest solution. The next wave reaching extreme eastern Siberia by about next Monday appears to have a tendency to dig southeast across southwestern Alaska by next Tuesday. The CMC mean offers the fastest solution regarding this wave. This solution appears much too fast when compared with the GEFS/EC mean consensus. The WPC forecast package was derived using 40% from the 12Z ECMWF/EC mean, 40% from the 12Z GFS/GEFS, and 20% from the 12Z CMC and CMC mean. More of the EC means were included early in the forecast period to avoid the fast EC solution of the digging wave over the Gulf of Alaska. A minimal amount of the CMC was included on Day 8 to avoid its fast solution with the second wave. The results are quite compatible with yesterday's forecast package, with a deeper surface low off to the south of the Panhandle from the weekend into early next week. ...Weather/Hazard Highlights... The highly amplified upper pattern in the vicinity of Alaska during the short-range period is forecast to break down as the medium-range period begins this Friday. The narrow plume of moisture that has brought snow across western Alaska is forecast to begin departing the North Slope and interior eastern Alaska on Friday. Dry conditions are expected to prevail through the weekend across much of Alaska with rather cold arctic air remaining in place over the Panhandle. The tight pressure gradient between the arctic high centered over northwestern Canada and the lingering low over the Gulf of Alaska could result in bouts of strong gusty winds from the southern coastline to the Panhandle through the forecast period. A slow increase in the chance of precipitation is seen across the Panhandle as both the offshore upper high and near-shore low retrograde further. The next wave forecast to dig toward Alaska early next week will be watched for the potential of increasing precipitation chance over Alaska, although model consensus supports that the dry conditions will continue. Kong Additional 3-7 Day Hazard Information can be found on the WPC medium range hazards outlook chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php WPC medium range Alaskan products including 500mb, surface fronts/pressures progs and sensible weather grids can also be found at: https://www.wpc.ncep.noaa.gov/alaska/ak_5dayfcst500_wbg.gif https://www.wpc.ncep.noaa.gov/alaska/akmedr.shtml https://www.wpc.ncep.noaa.gov/alaska/ak_5km_gridsbody.html